In the 1860s, with the rise of the ironclad ship and the
general improvement in shipboard armament, the coast defenses of the world had
been extensively overhauled in an attempt to keep pace. At the beginning
of this period the standard method of deploying coast guns was in open
batteries, but the advent of armor and powerful guns on ships led to the
adoption of armored forts in which guns were protected by casements with
enormous thickness of iron and granite to protect them. This was a very
expensive method of construction; a single armored casemate for one gun,
together with it's necessary magazine arrangements, cost over 3800 Pounds
(British Pounds Sterling), without the cost of the gun being considered.
Further, the slowness of the rate of fire of the heavy Rifled Muzzle-Loading
(RML) guns demanded the development and construction of large fortifications
with numerous guns to swamp the enemy with gunfire. Picklecombe Fort in Plymouth
Sound, for example, was prepared with forty-two armored casements, an expense of
160,000 Pounds, before the guns were installed. By way of comparison, the
Moncrief carriage and it's pit cost a mere 1345 Pounds, a considerable saving.
A second problem of the day, as with the Naval Ordnance Engineer, was that of
controlling recoil in confined spaces.

As early as 1835, Colonel DeRussey of the American army had
suggested mounting a gun on a form of standing carriage in which the wheels were
mounted eccentrically so that as it rolled back, it would descend behind the
fort's parapet for concealment. On the face of it, this was a fairly sound
idea, but one which was difficult to put into practice, largely due to the
difficulty of running the gun back into it's normal firing position.

All of the above problems and related factors were reconciled
in the design of a gun carriage put forward in late 1860s by Captain Moncrief of
the Edinburgh (Militia) Artillery.

Alexander Moncrief (1829-1906) was the son of an Officer in
the
Madras
Army (Presidency of Madras in India -- British East India Company). He
was born in
Edinburgh
, and after studies in the ancient universities of
Aberdeen
and
Edinburgh
, he spent some time in a civil engineer's office, but did not settle to a
profession, at that time. On
April 16, 1855
, he was commissioned into the Forfar and Kincardine Artillery (Militia) and
promptly went off on leave to the
Crimea
, where he watched the Russian guns being knocked out in the Mamelon Fort on
July 6, 1855
. The damage done by the shots put through the embrasures of that
fortification, inspired him to design a disappearing artillery carriage in 1868.

A previous design of a counterpoise carriage was proposed
about 1860. While theoretically sound the Buffington Carriage would have been
difficult to make up into an operational weapon, and it had to wait for
significant improvements before it would prove it's worth. This design is
shown below.

Moncrief's proposal was in the form of a counterbalanced gun
carriage. In 1871 twenty of these were issued. The gun, a 7 inch RML, was
mounted in a light carriage and this was connected to the top of a pair of
curved arms which could roll back on a lower carriage. The rear of this
gun carriage had two wheels which ran in an inclined plane. Thus, when the
gun was fired, the recoil forced it back so that the curved arm rolled and
allowed the wheels to run down the plane, bringing the gun below the level of
the parapet. A large counterweight was fitted to the bottom of the curved
arms to resist the force of the recoil, and this together with the curved face
of the arm brought the gun to rest where it was retained by a pawl.
Loading was now carried out under cover and then the pawl was released allowing
the counterweight to swing the gun up over the parapet into the firing position:

This provided a gun which was invisible from the sea until
the time came to fire, and which protected the crew while loading and serving
the piece was accomplished. The lower carriage could be moved to provide
traverse, and an arc and screw on the top carriage controlled elevation. The
only snag lay in the sights, which were still of the direct fore-sight and
back-sight type, which meant that the gunlayer had to leap up on the platform
and expose himself to lay and fire the gun. This was a small drawback though,
and the Disappearing Carriage (as this class came to be called) rapidly caught
the fancy of every nation looking for a suitable gun mounting.

This carriage design had three advantages:

1.It gave the gun crew protection from direct fire by
enabling the carriage to raise the gun to shoot over a solid parapet from a
lower position which was convenient for loading;

2.It stored the force of the recoil so that it could be used
to raise the gun back from the loading to the firing position;

3.The interposing of a moving fulcrum between the gun and
it's platform lessened the strain on the latter and allowed it to be of lighter
construction.

In Moncrief's first model a sub-carriage was used to keep the
gun at a constant angle as it disappeared. The counterweight at the foot
of the rolling arms was an iron box filled with several hundred-weight of
gravel.

Moncrief, in 1877, produced an improved version of his
mounting; the Mark II carriage for the 7 inch (17.8 cm) or 7 ton RML, (shown
below). This modification dispensed with the top carriage and slung the
gun directly on top of the "elevators" as the curved arms are now
known. The recoil pushes the gun on it's curved elevators back and downward to
the loading position, the energy of the recoil being used to raise a heavy,
cast-iron counterbalance weight, which can be used to return it to the firing
position. This improved carriage did away with the sub-carriage, and the
counterweight was made of massive iron blocks. Over eighty of these were
taken into service, and installed in British fortifications all over the world.
Later "disappearing" carriages employed hydro-pneumatic or hydraulic
recoil buffers.

In the
USA
, Captain (later General) Crozier of the Ordnance Department had taken an early
idea attributed to General Buffington, in which the gun was mounted on a
parallelogram, modified it and added hydraulic cylinders and a counterweight to
produce the Buffington - Crozier Disappearing Carriage. This modification
was the zenith of this kind of unit, Guns of 14 inch caliber were commonly
mounted on this carriage and the last and biggest were two 16 inch guns mounted
at Panama during the First World War and dismantled late in the Second World
War.

Moncrief transferred to the
Edinburgh
Artillery (Militia) in 1863, became a Major in 1872 while attached to the Royal
Arsenal Woolwich, and was made Colonel in 1878. He was elected a Fellow in
the Royal Society in 1871, and knighted in 1890.

The diagram below shows a British 13.5 inch Disappearing Gun.
This is the largest British gun to be mounted on a disappearing carriage.
Three were emplaced in the 1890s but they proved to be too complicated and were
withdrawn and scrapped in 1911.

The following illustration shows a diagram of a British
Hydro-Pneumatic Mounting. The Elswick Ordnance Company married the
hydro-pneumatic recoil buffer to the Moncrief principle and produced this
mounting which became the standard British pattern. Protected by a
nine-foot deep pit and an overhead shield, they were emplaced in British
defenses from
London
River
to
Hong Kong
.

The next diagram illustrates the Buffington-Crozier Mounting.
This was the acme of disappearing carriage design, the American coast defenses
mounted everything up to and including the 16 inch naval rifle on these
carriages. Taking Buffington's idea, Crozier turned it into a practical
device. The gun arms lift a massive counterweight and are damped by
hydraulic buffers at the pivot point, due to the gun arm pivots moving back.
The gun describes a complex path during recoil.

In the Royal British Navy in the 1880s another problem
surfaced. This was the problem of a balance of firepower on a ship between
broadside and frontal firing guns. An interesting attempt to solve the
problem was the "HMS Temeraire" completed in 1877 at the
Chatham
Naval Yard south of
London
,
England
. The design utilized in "Temeraire" was a central battery
structure, but in addition mounted two pivot guns, one at each end of the ship.
The pivot gun, had by this date fallen into disrepute due to the difficulty of
protecting it, but in the "Temeraire" this was solved by adopting a
device which had been originally developed for Coast Defense; the disappearing
carriage. It was this hydraulic carriage which was now adapted to naval
service in "Temeraire"; two carriages, each mounting a 12 inch RML gun
were used, one in each pivot gun position. Instead of the "pit"
of a land gun, these were protected by armored "barbettes", armor-
plated circular structures within which the guns could be worked and over
the top of which they were fired, recoiling down and behind the protection
between shots. Thus all-around fire was secured with protection.
However the "Temeraire" was never repeated; the hydraulic disappearing
carriage was a temperamental device at the best of times, cosseted by artificers
in fortress applications and undoubtedly prey to every defect that salt and
water could devise in a naval application. Further what the shifting
balance of a heaving ship would have done to the sensitive geometry of the
carriage is something about which the naval records are strangely silent.

The disappearing carriage had two drawbacks which were
insurmountable. One was the restricted elevation available -- the greatest
elevation ever managed by one of these designs was a mere 20 degrees and that
was not good enough for the new and powerful guns which were coming into service
at the end of the 1890s. The other drawback was the slow rate of fire due
to the time taken for the gun to swing up and down and be reloaded. In the
early days of coastal gunnery, shooting was a leisurely affair, but the
improvement in the speed of warships demanded an increased rate of firing and
the disappearing carriage was at a disadvantage compared with a gun which stayed
in position. Such a gun could be laid continuously on the target while
loading and firing went on. Another advantage of the stationary gun was
that the demand for protection was not now so great, since the more powerful
guns could keep enemy ships out at a range where they could hardly see the shore
weapons, particularly if some intelligence was applied to the matter of
concealment and camouflage.